Non-covalent Functionalized Carbon Nanotubes/MOFs Derivatives And Their Performance On Electrocatalytic Oxygen Evolution

As a clean and renewable energy source,hydrogen is of great significance to social development.Electrochemical splitting of water is a highly efficient and promising method for hydrogen production,and is a current hot spot of interest in the energy field.This method involves two main processes:cathodic hydrogen evolution reaction（HER）and anodic oxygen evolution reaction（OER）.Among them,OER is a four-electron-proton coupling reaction with high kinetic barriers,which is an important decisive speed step for electrolysis of water.Therefore,it is crucial to develop efficient catalysts to overcome the kinetic retardation problem associated with the complex multi-electron process.It was found that metal organic frameworks（MOFs）material derivatives have great potential to improve OER performance,but the low graphitization of carbon derived from ligands after thermal annealing treatment of MOFs and the poor binding interaction between metal nanoparticles（NPs）and derived carbon make it difficult to show the best performance in electrochemistry.The introduction of carbon nanomaterials,such as graphene or carbon nanotubes（CNTs）into MOFs derivatives can effectively improve their electron transport capacity and increase the effective mass diffusion pathway,which is an effective way to improve their OER performance.However,carbon materials often require concentrated acid oxidation treatment,resulting in the destruction of their intrinsic structures.Incorporating carbon nanomaterials with MOFs without their chemical treatment remains a challenge.To address this issue,in this paper,MWCNTs were non-covalently functionalized by a carbon nanomaterial dispersant,triethylenetetramine functionalized perylenimine（HAPBI-3）,and MOFs were grown in situ on the surface of MWCNTs while keeping their conductive substrates undamaged.further calcination in a tube furnace yielded the effect of different mass ratios of MWCNTs and the morphology of the composites on the electrocatalytic activity of OER was investigated.The main research contents and results of the paper are as follows.1.Non-covalent functionalization of MWCNTs by HAPBI-3,in situ growth of PMo₁₂@ZIF-67 on their surfaces,and calcination treatment to obtain highly efficient OER catalysts（CNT/Co/Co₆Mo₆C₂）.Firstly,MWCNTs were uniformly dispersed in water with HAPBI-3 as dispersant,and polyamino side chains were used as nucleation sites of MOFs after deprotonation to grow ZIF-67 in situ on the surface of MWCNTs.Meanwhile,PMo₁₂ was encapsulated in the cage structure of ZIF-67 using shipbuilding in a bottle method to form CNT/PMo₁₂@ZIF-67 composite structure.Compared with the mixed-acid oxidation method reported in the literature,this method does not destroy the intrinsic structure of MWCNTs.CNT/PMo₁₂@ZIF-67 was calcined under a nitrogen atmosphere to obtain the derivative CNT/Co/Co₆Mo₆C₂.the CNT/Co/Co₆Mo₆C₂ with 11.2%MWCNTs mass ratio in 1.0 M KOH exhibited the best OER catalytic performance.With an overpotential of only 308 m V at a current density of 10 m A cm^-2,the performance was better than other MWCNT ratios of CNT/Co/Co₆Mo₆C₂ and the same type of composites synthesized by PVP as surfactant assistance.The Tafel slope of this OER process is 70.9 m V dec^-1,and the electrode has a high bilayer capacitance(C_dl=42.3 m F cm^-2)as well as a large electrochemically active surface area(ECSA=1057.5 cm~2 _ECSA).This non-covalent functionalization method is beneficial for the enhancement of the material conductivity and OER electrocatalytic activity.2.HAPBI-3 was further modified with gallic acid（GA）to improve the dispersion of MWCNTs in methanol,which in turn led to higher performance OER catalysts by in situ growth and heat treatment.the reaction of GA with the amino group of HAPBI-3 can enhance the hydrogen bonding between molecules with methanol through the phenolic hydroxyl group.The coordination of phenolic hydroxyl groups with cobalt can also be used to grow PMo₁₂@ZIF-67 in situ on the surface of MWCNTs to form different CNT/PMo₁₂@ZIF-67.Compared with the previous chapter,the ZIF crystals synthesized by GA-APBI non-covalent functionalized in situ growth method showed further growth in particle size.This crystal enlargement facilitates the binding of more MWCNTs to the ZIF crystals and the calcination results in CNT/Co/Co₆Mo₆C₂composite nanocatalytic materials,which are also more favorable for the OER process.The overpotential of CNT/Co/Co₆Mo₆C₂ with 35%mass ratio of MWCNTs was only285 m V in 1.0 M KOH when the current density was 10 m A cm^-2,and the performance was much better than using other dispersants such as polyvinylpyrrolidone（PVP）,cetyltrimethylammonium bromide（CTAB）,sodium dodecyl sulfate（SDS）and dodecylbenzene sodium sulfate（SDBS）to disperse similar catalytic materials synthesized by MWCNTs.This non-covalent functionalization method allows the construction of uniformly distributed nucleation sites on the surface of carbon materials,thus growing MOFs in situ on their surfaces,enhancing the conductivity of the composite derivatives and improving the utilization of catalytic active sites.This new method provides a new idea for the synthesis of nanocarbon-doped electrocatalytic materials with great potential for electrochemical applications.